Field
The present disclosure relates generally to communication systems, and more particularly, to an apparatus and method for linearizing a baseband filter.
Background
A wireless device (e.g., a cellular phone or a smartphone) may transmit and receive data for two-way communication with a wireless communication system. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a transmit local oscillator (LO) signal with data to obtain a modulated radio frequency (RF) signal, amplify the modulated RF signal to obtain an output RF signal having the desired output power level, and transmit the output RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna, downconvert the received RF signal with a receive LO signal, and process the downconverted signal to recover data sent by the base station.
There is an increasing demand to have wireless devices capable of high-quality transmission and reception while consuming low power. One key to achieving high quality is associated with the performance of the device's transmitter. For example, it is desirable to have a transmitter that operates efficiently over its entire output power range.
In existing transmitter designs, a baseband (BB) filter and upconverter (mixer) are used to filter a baseband signal and up-convert the filtered signal to radio frequencies (RF) for transmission. Typically, both the baseband filter and upconverter are configured to operate across the entire output power range to meet stringent linearity requirements at maximum power. However, the existing transmitter designs that linearize the baseband filter may provide limited noise performance and/or power performance. Such existing transmitter designs may also inefficiently utilize a device area due to the use of modules/elements that consume a relatively large portion of device area. It is therefore desirable to have a more efficient scheme for linearizing the baseband filter for use in wireless devices.